Browsing by Author "Hager, Philipp B."
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Item Theoretical Approach to Quantify Effects of Lunar Dust Deposition on Radiator Performance for Moon Exploration Missions(2023 International Conference on Environmental Systems, 2023-07-16) Hager, Philipp B.; Tighe, Adrian P.; Cipriani, Fabrice W.S.; McDonald, FrancescaIn this paper a set of theoretical equations is presented, derived from data published in the literature, which allow the conversion between lunar dust deposition rates and the modification of thermo-optical properties of radiators for lunar surface missions. This work is supporting the early design phases of Argonaut. Lunar dust and its effect on thermal control hardware is a large unknown when designing hardware for lunar surface missions. There are natural and artificial dust levitation and transport processes such as landing or roving vehicles or naturally occurring electrical charge differences. These cause the dust to move across the surface of the Moon and deposit. The smallest fraction of the sharp-edged small dust particles easily deposits on and adheres to technical surfaces, such as radiators or MLI. Literature on dust deposition is based on flight data and hence linked to natural lunar regolith, whereas the literature on radiator thermo-optical property modification is mostly based on tests performed with lunar dust simulant (LDS) materials. For both dust deposition and property modification, literature is scarce. The particle size distribution, density, particle shape, mineralogy, and thermo-optical properties of the natural and dust simulants differ and impact the conclusions. Solar absorptivity of radiators is more affected than its infrared emissivity. Applying the approach described in this paper, the data from literature leads to a modification factor for the solar absorptivity that varies from 1.1 to almost 5 for natural lunar dust deposition ranging from 140-840 µg/cm2, but depends on type of radiator coating, and radiator substrate. The same dust coverage rate of 25% can lead to modification factors for solar absorptivity that range from 1.4 @ 1790 µg/cm2 to 2.6 @ 840 µg/cm2, depending on the applied conversation from natural lunar dust to LDS and the selected material properties. The conducted study is meant as a first steppingstone toward design guidelines for thermal engineers for ‘dusted end-of-life’ properties for thermal control coatings.Item Traverse Planning on the Lunar Surface – Benefits from Thermal Modeling(45th International Conference on Environmental Systems, 2015-07-12) Killian, Matthias; Hager, Philipp B.Classic traverse optimization methods focus on energy demands for driving only. The subject of this work is to identify potential for future traverse optimizations in lunar environments by combining thermal modeling with classic optimization methods related to locomotion energy. For this purpose five different traverses are investigated that share the same starting and final point on two sides of a lunar crater. For the simulations presented in this paper, an in-house developed lunar specific thermal preprocessor creates the lunar scenery, the moving sample object, and its traverses in a geometrical and nodal representation. The commercial software package ESATAN-TMS performs the thermal calculations afterwards, starting with ray tracing and finishing with solving the entire nodal network. Rovers can profit from traverse optimization by increasing the mission lifetime or the exploration area because of power savings in the thermal control subsystem. The analysis of all simulated traverses focuses on energetic aspects: energy needed for locomotion, energy needed for thermal control, and possible energy acquired by solar cells. Traverses differ in their distance between two points, the period in shadow and the terrain slope in the same artificial lunar setting. In order to estimate the influence of thermal design, the five traverses were analyzed with three different rover configurations. Results show that energy savings ranging from 32 % to 83 % are possible compared to the shortest traverse, dependent on the rover configuration and the traverse. A longer travel time has to be taken into account for such energy savings.